The inventor of the present application proposed, in U.S. Pat. No. 6,204,545, a spherical semiconductor element which has a light-receiving or light-emitting function, wherein a spherical pn-junction is formed near the surface of a spherical semiconductor crystal, and dot-shaped positive and negative electrodes are formed at both ends across the center of the spherical crystal. The semiconductor element has optical symmetry in other directions than the axial direction connecting the pair of electrodes, and has the advantage that it can receive light three-dimensionally from various directions and emit light three-dimensionally in various directions.
The inventor of the present application proposed, in International Laid-Open Patent Application WO03/017382, a spherical semiconductor device which is nearly the same semiconductor element as said semiconductor element, wherein one electrode is formed on a flat surface with a part of an apex of a spherical semiconductor crystal removed, and the other electrode is formed on the opposite side of the electrode across the center of the semiconductor crystal.
A light-receiving or light-emitting module is obtained by arranging such spherical semiconductor elements in a planar matrix form with many rows and columns, serially connecting multiple semiconductor elements in each column, and connecting in parallel multiple semiconductor elements in each row. The larger the light-receiving area or light-emitting area of the module is made, the larger the number of connecting points at which the semiconductor element is electrically connected becomes.
The inventor of the present application proposed, in International Laid-Open Patent Application WO02/35612, a spherical semiconductor device which is nearly the same semiconductor element as said semiconductor element, wherein a pair of flat surfaces are formed by removing both ends across the center of a spherical semiconductor crystal, a pn-junction is formed near the surface including one flat surface of the semiconductor crystal, and positive and negative electrodes are formed on the one flat surface and the other flat surface.
In addition, proposed in International Laid-Open Patent Application WO02/35612 is a rod-shaped semiconductor element which has a light-receiving or light-emitting function, wherein a pair of end surfaces is formed perpendicular to the shaft on a columnar semiconductor crystal, a pn-junction is formed near the surface of the semiconductor crystal including one end surface, and positive and negative electrodes are formed on both of the end surfaces. The rod-shaped semiconductor element has an optical symmetry in other directions than the axial direction connecting the pair of electrodes, and has an advantage that it can receive light three-dimensionally from various directions and emit light three-dimensionally in various directions.
In the photovoltaic array described in U.S. Pat. No. 3,984,256, an n-type diffusion layer is formed on the surface of a filament made of p-type silicon semiconductor of 0.001˜0.010 inches in diameter, a plural number of this filament are arranged in parallel and in a planar form, multiple P-connection line members and N-connection line members are alternately placed orthogonally on the top of these filaments, the P-connection line member is ohmic-connected to the exposed part of the p-type silicon semiconductor of multiple filaments, the N-connection line member is ohmic-connected to the n-type diffusion layer of multiple filaments, multiple P-connection line members are connected to a P bus, and multiple N-connection line members are connected to an N bus. An insulating fiber with a superior strength is woven in so as to constitute multiple P buses and N buses and a mesh, thus constituting a flexible solar battery blanket which generate electricity by receiving incident light from its top surface.
In the semiconductor fiber solar battery and module described in U.S. Pat. No. 5,437,736, a molybdenum conductive layer is formed on the surface of an insulating fiber, two layers of p-type and n-type thin-film semiconductor layers having a photovoltaic function and a ZnO conductive layer are formed on approximately ⅗ of the periphery of the surface of this conductive layer, a plural number of these semiconductor fiber solar batteries are arranged in parallel and in a planar form, a metal coating is formed on its backside, after which the metal coating is partially removed in a specified pattern, thus forming a connection circuit which performs tasks such as serially connecting multiple semiconductor fiber solar batteries.
Patent Document 1: U.S. Pat. No. 6,204,545.
Patent Document 2: International Laid-Open Patent Application WO03/017382.
Patent Document 3: International Laid-Open Patent Application WO02/35612.
Patent Document 4: U.S. Pat. No. 3,984,256.
Patent Document 5: U.S. Pat. No. 5,437,736.
In manufacturing a solar battery panel using spherical semiconductor elements, a near-spherical semiconductor elements with a flat surface formed on a part of each, or near-spherical semiconductor elements with a pair of flat surfaces formed, the number of connecting points which electrically connect the semiconductor elements increases, the structure of a conductive connection mechanism which electrically connects the semiconductor elements becomes complex, and its manufacturing cost increases.
Because said rod-shaped semiconductor element also has a granular shape, in manufacturing a solar battery panel, the number of connecting points which electrically connect the semiconductor elements increases, the structure of a conductive connection mechanism which electrically connects the semiconductor elements becomes complex, and its manufacturing cost increases.
Furthermore, because a pair of electrodes are formed on both end surfaces perpendicular to the shaft, if the length of the rod-shaped semiconductor element is made large, the distance between the positive and negative electrodes increases, and the electrical resistance between the positive and negative electrodes increases. Therefore, the rod-shaped semiconductor element is not fit for manufacturing a semiconductor element having a length multiple times that of the diameter.
Because the photovoltaic array described in U.S. Pat. No. 3,984,256 has a construction wherein light enters from the top in the same manner as solar battery panels installed near-horizontally, it cannot receive light entering from both sides of the panel. This is also true with the semiconductor fiber solar battery in U.S. Pat. No. 5,437,736.
Especially, in a solar battery panel embedded in a window glass for example, it is desired that it be able to receive light from both sides. On the other hand, in constructing a light-emitting panel with semiconductor elements having a light-emitting function, it is desirable that light can be emitted to both sides of the panel.
Objectives of the present invention include providing a rod-shaped semiconductor element which has a light-receiving or light-emitting function and can increase the light-receiving area without increasing the inter-electrode distance, providing a rod-shaped semiconductor element which has a large length/diameter ratio and can reduce the number of electrical connecting parts in making a panel of multiple semiconductor elements, providing a rod-shaped semiconductor element which is hard to roll, providing a rod-shaped semiconductor elements wherein polarity of each electrode is easy to identify, and so on.
The rod-shaped semiconductor device of the present invention, having a light-receiving or light-emitting function, comprises a rod-shaped substrate made of p-type or n-type semiconductor crystal having a circular cross section or near-circular cross section, a separate conductive layer which is formed on a part of a surface of the substrate excluding a band-shaped part parallel to an axis of the substrate and has a different conduction type from that of the conduction type of the substrate, a near-cylindrical pn-junction formed with the substrate and the separate conductive layer, a band-shaped first electrode which is ohmic-connected to a surface of the band-shaped part of the substrate, and a band-shaped second electrode ohmic-connected to the separate conductive layer on an opposite side of the first electrode across the axis of the substrate. The separate conductive layer may be formed by diffusion, film formation, or ion injection.
If the rod-shaped semiconductor device has a light-receiving function, when sunlight is received, it generates a photovoltaic power of a specified voltage by its pn-junction, and outputs it between the first and second electrodes. Because it has a light-receiving symmetry about a plane which includes the first and second electrodes, light beams entering from both sides of the plane are received to generate electric power. If a large number of rod-shaped semiconductor devices are arranged in a panel shape and a circuit to extract the output is formed, it becomes a solar battery panel (solar battery module).
If the rod-shaped semiconductor device has a light-emitting function, when a specified voltage is applied between the first and second electrodes, light corresponding to the band-gap energy from the pn-junction is emitted from the pn-junction. If a large number of rod-shaped semiconductor devices are arranged in a panel shape and a circuit to apply a voltage is formed, it becomes a light-emitting panel (light-emitting module).
According to the rod-shaped semiconductor device of the present invention, because band-shaped first and second electrodes connected to the surface of a band-shaped part of a rod-shaped substrate and a separate conductive layer are installed, even when the length/diameter ratio of the substrate is increased, the distance between the first and second electrodes can be maintained smaller than the diameter of the substrate, and the electrical resistance between the first and second electrodes can be maintained small. Therefore, power generating performance or light-emitting performance in the pn-junction can be maintained high.
As a result, in constructing a light-receiving or light-emitting panel, the light-receiving area of each semiconductor device is increased by increasing the length/diameter ratio of the substrate, and the number of electrical connecting parts for wiring the semiconductor devices can be decreased, making it possible to improve the reliability of the panel and reduce the manufacturing cost. Furthermore, because there is a light-receiving or light-emitting symmetry about a plane including the first and second electrodes, it is possible to construct a light-receiving panel which can receive light from both sides of the panel or a light-emitting panel which can emit light from both sides of the panel.
As the constitutions of dependent claims of the present invention, various kinds of constitutions such as the following may be adopted.
(1) A band-shaped apex of the substrate is removed to form a band-shaped flat surface, and on this flat surface the band-shaped part is formed, not only making it a rod-shaped semiconductor element which is hard to roll, but also making it possible to easily identify the polarities of the first and second electrodes.(2) An antireflective film is formed on a part of the surfaces of the substrate and separate conductive layer excluding the first and second electrodes.(3) The substrate is made of p-type Si single-crystal or Si polycrystalline, and the separate conductive layer is made of an n-type conductive layer containing P, Sb, or As.(4) The substrate is made of n-type Si single-crystal or Si polycrystalline, and the separate conductive layer is constituted of a p-type conductive layer containing B, Ga, or Al.(5) The device is constructed to be a light-receiving device which receives light and generates electricity.(6) The substrate is made of n-type GaP single crystal or GaAs single crystal, and the separate conductive layer is constituted of an n-type diffusion layer wherein Zn is thermally diffused, which constitutes a light-emitting diode.(7) The substrate is made of n-type GaAs single crystal, and the separate conductive layer is formed by diffusion, film-forming, or ion-injection of p-type GaAs, which constitutes a light-emitting diode.(8) The substrate is made of n-type SiC single crystal, and the separate conductive layer is formed by forming a p-type GaN, GaInP, or P film, which constitutes a light-emitting diode.(9) The area of the pn-junction is set larger than the area of a cross section perpendicular to the axis of the substrate.